Air-break disconnecting switches



Oct. 10, 1961 J. w. SKOOGLUND 3,004,11 7

AIR-BREAK DISCONNECTING SWITCHES Filed April 30, 1958 3 Sheets-Sheet 1 Fig. 3.

W'TNESSES: 36 J h I d o n oog un C C) [Ia/ED BY 4%). 68M ma 6w):

ATTORNEY Oct. 10, 1961 J. w. SKOOGLUND 3,004,117

AIR-BREAK DISCONNECTING SWITCHES Filed April 50, 1958 S Sheets-Sheet 2 Fig.5. I Fig.6. 24

so s4 42 '54; 7 4

Fig. 7.

Oct. 10, 1961 J. w. SKOOGLUND 3,004,117

AIR-BREAK DISCONNECTING SWITCHES Filed April 50, 1958 5 Sheets-Sheet 3 Fig.9.

United States Patent O 3,004,117 AIR-BREAK DISCONNECTING SWITCHES John W. Skooglund, North Huntingdon, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 30, 1958, Ser. No. 732,078 20 Claims. (Cl. 200-48) This invention relates, in general, to air break disconnecting switches having associated therewith a series impedance assembly inserted into circuit during the opening operation, and, more particularly, to such air-break disconnecting switches of the foregoing type having improved constructional features to minimize, or prevent, high transient overvoltages on the connected lines during switching operations.

A general object of the present inventionis to provide an improved air-break disconnecting switch having a series impedance inserted into series circuit during the opening operation, in which improved arcing contact structures are provided to facilitate arc transfer, to grade the voltage axially along the impedance assembly, and to prevent corona formation during high-voltage operation of the switch. Particular advantage is obtained by the use of series resistor sections incrementally inserted into series circuit during the opening operation of the switch, but by-passed in the closed-circuit position of the switch.

Another object of the present invention is to provide an improved switching arrangement for an air-break dis connecting switch.

A further object of the invention is to provide an improved series resistor assembly, which may be adapted to airbreak disconnecting switches extending over a wide voltage range.

Yet a further object of the present invention is to provide an improved air-break disconnecting switch in which a series resistor assembly is associated therewith in such a manner that cantilever stresses and cable whipping will not cause misalignment of the contact structure.

Another object of the present invention is to provide an improved resistor assemblage for a resistor-equipped, air-break disconnecting switch in which the resistor elements are located within a hollow casing filled with a high-dielectric-strength gas to prevent voltage breakdown.

Still a further object of the invention is to provide improved arcing contacts serving as corona shields along the resistance assemblage. of a resistor-equipped, air-break disconnecting switch.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 is a perspective view of an air-break disconnecting switch equipped with a seriesresistor assembly in accordance with the principles of the present invention, and the movable switch blade being illustrated in the open-circuit position;

FIG. 2 is a side elevational view of the resistorequipped, air-break disconnecting switch of FIG. 1, the contact structure being illustrated in the closed-circuit position;

FIG. 3 is a fragmentary sectional view taken along the line IIIIII of FIG. 2;

FIG. 4 is a fragmentary plan view taken along the line IVIV of FIG. 2;

*IG. 5 illustrates a modification of the invention involving the incorporation of a series-resistor assembly to a switch of relatively low-voltage rating; 7

FIG. 6 is a fragmentary side elevational view of a modified type of air-break disconnecting switch'incorporating principles of the present invention, the switch being of a lower voltage rating than the disconnecting switch of FIG. 1;

FIG. 7 is an enlarged, fragmentary view of one of the resistor sections illustrating the weather-proof casing therefor, and some of the internal constructional features thereof;

FIG. 8 is a fragmentary, side elevational view of a resistor-block stack, constituting a resistor section, which is inserted into the hollow casing of the resistor section of FIG. 7, and illustrating certain constructional features;

, FIG. 8A is a plan view of a V-shaped metallic spacing element employed in the resistor stack of FIG. 8;

FIG. 8B is a plan view of another metallic spacing element used in the resistor stack of FIG. 8; and

FIG. 9 somewhat diagrammatically illustrates a modification of the present invention utilizing a high-dielectricstrength gas interiorly of the resistor sections.

In the operation of an electric utility system there has existed for many years a need for equipment to fill the void that was present between power circuit breakers with fault interrupting ratings and the air-break switch which has no interrupting rating and which has a very limited interrupting ability. Air-break switches are designed simply to isolate other equipment for maintenance purposes or to sectionalize power systems, and generally speaking these switching operations are performed with the system deenergized.

. While the switches have no guaranteed interrupting rating, they are frequently called upon to interrupt on arcing horns, small amounts of line charging current, transformer magnetizing current, or even light parallel load currents. This operation of air-break switches to interrupt these small amounts of currentcan be fairly successful if weather conditions are favorable and if the operator has made certain that the current to be interrupted is small. This sort of operation is accomplished regularly, although admittedly it is a gamble. An interesting summary'of the experiences of fifty-nine utilities is presented in AIEE technical paper 51-113. This paper is the report of a working group which polled the utilities and summarized the data which was sup plied. It shows that the actual percent of successful operations ranges from 50% to depending on magnitudes of voltage and current which are involved as well as the uncontrollable weather factor.

It is evident, then, that under the most favorable conditionsthis type of operation for an air-break switch is not an assured success, and a hazard to equipment, personnel, and continuity of service definitely exists where there is uncontrolled arcing. The inherent nature of unconfined arcs to wander in long circuitous paths and travel with the slightest wind providesno assurance that the arcing, attendant with opening an air-break switch,

will not bridge phase to phase or involve groundedstructural members.

From the standpoint of economics the electric utility company cannot justify the cost of a power circuit break-. er with fault interrupting ability simply to handle the infrequent switching of 10 to 15 amperes. The need for a low-cost load-switching device is quite apparent. I

With the installation of 345 kv. systems the problem of switching surges has become prominent, and a simple and effective means has been devised to eliminate these surges which have proved damaging to other equipment on the system. This is not a problem of circuit interruption but it is certainly closely related to it. The surges occur when switching capac-itive'typc circuits involving station cable-charging currents or transmission-line charging currents. When opening a switch on such a circuit,

. restrikes have been observed which have caused as many as 43 lightning-arrester operations during one three-phase switch opening.

A solution to this problem, as set forth hereinafter, is

not to try to interrupt the are, but simply to insert resistance in the are path and thereby dissipate are energy and keep the voltage oscillations to normal levels. An ohmic resistance value which is several times the surge impedance of the system is desirable, as set forth and described in United States patent application by Samuel B. Griscom, filed April 24, 1958, Serial No. 730,692, and assigned to the assignee of the instant application.

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally desig' nates an air-break disconnecting switch suitable for the sectionalizing of relatively high-voltage circuits, and in eluding a base 2, insulating columns 3, 4, 5 and 6 supporting the contact elements of the disconnecting switch. As illustrated, insulating columns 3 and 4 carry a mechanism housing member 7, having disposed therewithin a cam operating mechanism suitable for effecting the opening and closing, swinging motion of a movable disconnecting blade 8.

The actuating. mechanism disposed interiorly within the housing 7 may be of any suitable type, and constitutes no part of the present invention. One such type, which may be used, is that set out in United States Patent 2,436,296, issued February 17, 1948, to Howard W. Graybill and Paul Olsson and assigned to the assignee of the instant application. The actuation of such mechanism may be effected by the rotation of the insulator column 4. The actuation of this mechanism will be effective to cause clockwise, swinging motion of the switch blade 8 from its fully opencircuit position, shown in FIG. 1, down into engagement with a stationary jaw contact 10, more clearly shown in FIG. 2 of the drawings. Subsequently, the blade 3 is rotated axially into firm contacting engagement. FIG. 2 illustrates a side elevational view taken on the opposite side of the switch shown in FIG. 1.

As illustrated in FIGS. 1 and 2, the stationary jaw contacts 10 are supported at the upper end of the insulator column 5. Electrostatic side shielding or corona rings 11, constituting a break-jaw corona shield, are disposed on opposite sides of the stationary contact 10, as more clearly shown in FIG. 3 of the drawings. Electrically connected to the stationary jaw contact 10, by braided conductors 12, is an upstanding, sectional impedance or resistor assembly, generally designated by the reference numeral 13, and having a configuration more clearly shown in FIGS. 1 and 2. The sectional, impedance assembly 13 may be composed of three resistance sections A, B and C. Additional impedance sections, if desired, may be superimposed upon those illustrated, as will be obvious to those skilled in the art.

Each resistor section 14 generally comprises a weatherproofhollow casing 15 (FIG. 7), interiorly of which is stationarily positioned a carbon-block resistance stack, generally designated by the reference numeral 16, and more clearly illustrated in FIG. 8 of the drawings.

With reference toFIG. 7, it will be noted that the hollow casing 15, which preferably is made of porcelain, having skirts 15a for a long creepage path, provides an internal hollow space 17, within which is positioned the carbon-block resistance stack 16 of FIG. 8.

A supporting flange means including a cap casting 19 is cemented to the upper end of hollow porcelain casing 15, and a lower base casting 20 is likewise cemented and secured to the lower end of porcelain casing 15. Inserted interiorly within the space 17 is the carbon-block resistance stack 16 of FIG. 8, which comprises a plurality of carbon blocks 21 spaced apart by diaphragm-shaped metallic stop assemblies 2 2. Also metallic V shaped spacers 23 are employed, cut the proper vertical lengths from conducting sheet metal, to space the resistor blocks 21 the proper distance apart. FIG. 8A shows a plan view of such a spacing element 23. FIG. 8B shows a plan view of top metallic sleeve-like spacing element 24. As an example, twelve such resistor blocks 21 may be provided along a singleresistor stack 16. The carbon blocks 21 have the characteristic of dissipating considenable heat, and can withstand thermal shock. In addition, they have the characteristic of being linear in their response to voltage.

Adjustably secured by adjusting means or clamps 25 (FIG. 4) to the porcelain-casing end cap castings 19 are oval-shaped corona shields, or arcing rings 36, disposed adjacent the upper end of the resistor assembly 13, and hence disposed at opposite ends of the upper resistance section C. A stub electrode 28, more clearly shown in FIG. 3, is disposed at the upper end of resistance section A. With reference to FIG. 3, it will be noted that in conjunction with stub electrode 28, an oval resistance ring 29 is employed. At the lower end of resistance section A are disposed a terminal pad 30 and a second oval ring 29.

It will be noted that the diameter or lateral dimension of the movable corona ball 31 attached to and movable with the free end of the swinging movable switch blade 8 is less than the vertical spacing between the stub electrode 28 and the lower lower arcing ring 36, or between the two arcing rings 36 at the upper end of the resistor assembly 13.

During the opening operation the insulator column 4- is rotated. This actuates the mechanism, disposed within mechanism housing 7, to first effect axial icefreeing and contact-pressure-redueing rotation of switch blade 8 and subsequently upward, arcuate movement of the end 31 of movable disconnecting switch blade 8 along an arc of travel indicated by the reference numeral 32 in FIG. 2 of the drawings.

Upon the separation of the end 31 of disconnecting blade 8 from stationary jaw contact 10, a small arc is drawn from the ends of the break jaws 10 to the blade tip 31. The are lengthens until the blade tip 31 passes the first corona shield, or arcing contact 28 on the resistor assembly 13. When, for example, the gap from the blade tip 31 to the first corona shield 28 decreases to approximately two inches, the are transfers readily to the arcing contact 28 leaving the break jaw contact 10, and thereby inserts the first section 14- of the resistor assembly 13 into series with the arc path.

As the blade 8 continues to rise, the are lengthens between the first electrode 28 and the blade tip 31 until the tip S31 approaches the second arcing shield 36. Again, due to the decrease of the gap in air, the are transfers to this second arcing shield 36, thereby inserting the second increment of resistance into series with the are. This occurs at a gap separation slightly longer than for the first arc transfer, approximately three inches.

Thesame process is repeated as the blade 8 swings toward the top of the resistor assembly 13. The are transfers to the top corona shield 36 when the blade tip 3 1 approaches to within about eight inches of this electrode. When this point is reached, the entire resistance is inserted into the arc path.

As the blade 8 continues to rise still further, the arc lengthens until it can no longer sustain itself and is extinguished. This occurs when the gap between the blade tip 31 and the top electrode 36 is about 24 to 30 inches, for example, on a 345 kv. switch.

In this manner, the resistance is inserted incrementally into circuit, and the arc length minimized untilthe entire resistance is in the circuit. The sequence reverses during the closing operation, and when the switch is completely closed the resistance assembly is bypassed.

An important advantage of the construction illustrated is that during'switch operation a gap distance exists at all times between the end 31 of switch blade 8 and the arcing contacts 28, 36. If a sliding, or otherwise physically engaging contact were had between the arcing contacts 28, 36 and a contact at the end of switch blade 8. the initial, axial, ice-freeing and contact-pressurc-reducing rotation of switch blade 8 would:be accompanied:

withdifliculty in providing proper sliding engagement during the opening operation. Q

Also, it must be. remembered that frequently this initial axial rotation of switch blade 8, during the opening operation, continues during a portion of the opening, separating motion of switch blade 8 away from its cooperating stationary contact 10. Such continued, axial ro tation would provide, of course, additional complications if a slidingcontacting engagement were employed. As shown, however, the gap distance between arcing contacts 28, 36 and the end 31 of switch blade 8 avoids any such difficulties.

As mentioned, the resistor assembly 13 consists of carbon-block resistors 21 mounted within "a sealed porcelain weather casing 15. Each unit assembly 14 is designed for stacking one on the other. In order to coordinate the resistors with the disconnect switch, as described previously, an arcing contact connected electrically to the resistor elements is mounted at each flange of the stacked assembly. In the higher voltage ratings, such as the 345 kv. switch illustrated in FIGS; 1 and 2, the arcing contacts 28, 36 also serve as corona shields. The arcing contacts 36 are adjustable so that they may be coordinated with the path of travel 32 of the main switch blade. The resistor assembly 13 is designed to have adequate thermal capacity to withstand repeated switch'operation without damage, it being noted that the carbon-block resistor or impedance elements 21 carry current only during the opening and closing operations of the switch 1.

FIG. illustrates a modified resistance assemblage involving only two resistance sections X and Y having wire or rod-shaped arcing electrodes 33 and 34. It will be noted that for the lower rating device, as illustrated in FIG. 5, say for 115 to 161 kv. voltage range, the resistance assembly 37 may be mounted upon the same insulator stack 9 as supports the jaw contact 38. The movable disconnect blade 39 is of slightly modified construction, from that illustrated in FIG. 2, having a hookshaped wire 'or rod end 41). Again it will be noted that the lateral dimension of the hook-shaped rod end 40 of the switch blade 39 is less than the vertical spacing between the electrodes 33, 34. The arcuate paths of travel for the 115 kv. switch blade 39 and for the 161 kv. switch blade 39 are respectively indicated by the dotted lines 42, 43. I

FIG. 6 illustrates a modified type of switch, somewhat similar to that of FIG. 5, but incorporating modified arcing electrodes 45, 46. The rod-shaped arcing electrodes 45, 46 extend laterally from a junction cast-ing 18 and a top cover casting 24 respectively. Again the lateral dimension of the hook-shaped rod end 40 is less than the vertical spacing between the electrodes 45, 46. The modified resistance assemblage 47 is, inthis particular instance, adapted for support upon a separate insulator stack 48. Paths of Switchblade travel for 196 kv. and 230 kv. are respectively indicated by the dotted lines 49, 50.

FIG. 9 illustrates a modified type of construction in which the resistor sections, generally designated by the reference numeral 51, are disposed within modified hollow gas-tight weatherproof casings 52 containing a highdielectric-strength gas, such as sulfur hex-afluoride (SF By having the resistors 51 mounted in hollow casings 52 and surrounded by an atmosphere of such high-dielectricstrength gas, the resistance sections 51 have a very high voltage-withstanding ability, say approximately 2 /2 times system line to neutral crest. Also, by surrounding the resistor sections 51 with an atmosphere of sulfur hexafluoride (S F a high-voltage-withstanding ability may be obtained with a very short physical length Umbrellashaped shielding rings 70, 71 facing each other across the resistance sections 51, constituting an impedance assemblage 53, serve as arcing contacts. The shielding rings 70, 711, in addition to the central arcing ring'72,

the circuit components and the voltage.

grade thevoltage uniformly along the assemblage 53; The final break is made at arcing contact 60. As set out above, and with reference to FIG. 9, it will be apparent that the invention contemplates the use of sulfur hexafluoride (SP gas, or other suitable high dielectric strength gas, as a high-dielectric-strength gas to enable the resistor sections, 51, disposed within the hollow casings 52; to withstand very high voltage. Also, since the hollow porcelain casings 52 of FIG. 9 are subjected to voltage for only a short period of time, they may have a very simple physical structure. Service contamination is no problem.

As'stated, when the disconnecting switch isclosed, the

resistor assembly is bypassed, and no load current flows through its circuit. During the opening operation, the arc transfers to the arcing contacts associated with the resistor assembly and incrementally inserts resistor sections serially into circuit, which consequentlyreduces the magnitude of the transient over-voltage. When the arc is lengthened between the top arcing contact 60, it is quickly extinguished. It will be noted that the grading rings on the resistor assembly serve a dual function. First, they serve the function of arcing contacts as the arc is transferred from the stationary disconnecting contact up the resistor assembly to the uppermost arcing contact. Secondly, the grading rings distribute the voltage across the resistor assembly and prevent arcing to the resistor assembly porcelain or center connection. All fittings on the resistor assembly should preferably have smooth edges, and the grading rings are preferably used to reduce voltage stress and minimize formation of corona.

From the foregoing description, it will be apparent that there is provided an improved air-break disconnect ing switch having a series resistance assemblage in which the arcing electrodes 28, 36 are spaced away from the path of travel of the tip 31 of the movable switch blade 8. This separation distance insures that any formation of ice will not interfere with proper switch operation. In addition, any lateral movement of the resistance column 13 will not cause misalignment of the contacts, which might occur if there were an actual physical or sliding contact between the tip 31 of the switch blade 18 and the arcing electrodes. 21, 36. Moreover, it will be apparent that the corona rings 29, 36 assist in grading the voltage lengthwise along the impedance assemblage 13, thereby compelling each resistance section 14 to assume its fair share of the total voltage. Additionally, the employment of the arcing rings 29, 36 prevents corona formation at the interiorly disposed, relatively sharp, contacting parts of the cap castings 19.

' Th particular numerical value of the resistance in ohms employed in the resistance assemblage 13 depends upon Its electrical dimensioning is set out in detail, and claimed in the aforesaid patent application of Samuel B. Griscom. Generally, the resistance value is preferably several times the surge impedance of the circuit connected to the disconnecting switch.

From the foregoing description, it will be apparent that the present invention provides a solution to the problem of high-voltage, air-break disconnecting switches being employed to switch long lengths of bus and yet avoiding the formation of higs: transient over-voltages. The prior art disconnecting switches, operating in air, caused a large number of restrikes to occur before the arc was finally extinguished. The restrikes and the accompanying overvoltages, of course, imposed severe operating duty upon the connected lightning arresters, transformers and circuit breakers. By anapplication of the present invention, the particularly severe duty imposedupon such lightning arresters can be avoided.

By housing the resistors within hollow porcelain structures, they are physically supported and also electrically insulated. Thus there is no icing problem and contamination presents no difiiculty.

' Although there have been illustrated and described specific embodiments of air-break disconnecting switches suitable for various voltage ratings, it is to be clearly understood that the same were merely for the purpose of illustration and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

I claim as my invention:

1. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including one or more impedance sections, an arcing contact at one end of at least one impedance section to which the are upon opening switch movement may terminate yet spaced from 'said arcuate path of travel, and said arcing contact including a substantially oval-shaped arcing ring disposed in a plane substantially normal to the axial length of the impedance assemblage.

2. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including one or more impedance sections, an arcing contact at one end of at least one impedance section to which the are upon opening switch movement may terminate yet spaced from said arcuate path of travel, said arcing contact including a substantially oval-shaped arcing ring disposed in a plane sub stantially normal to the' axial length of the impedance assemblage, and adjusting means for adjustably moving said arcing ring laterally with respect to the impedance assemblage to vary its spacing from said path of travel.

3. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including one or more impedance sections, conducting structure at one end orf at least one impedance section, a surrounding generally ring-shaped arcing contact connected to said conducting structure and electrostatically shielding said conducting structure to prevent corona formation at the latter, said generally ring-shaped arcing contact being spaced from said arcuate path of travel, and said generally ringshaped arcing contact being disposed in a plane which is generally normally of said impedance assemblage.

4. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, means effecting an axial contact-pressure-reducing rotation of the switch blade during the initial portion of the opening operation, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including one or more impedance sections, one or more insulating hollow weatherproof casings, a stack of impedance elements disposed interiorly within at least one hollow weatherproof casing, a high-dielectric-strength gas disposed within said one hollow weatherproof casing to prevent voltage breakdown axially of said stack of impedance elements, a plurality of arcing contacts tapped into said impedance assemblage to insert impedance serially into circuit dur-- ing the opening operation, the arcing contacts being spaced from said arcuate path of travel, the lateral dimension of the free end of the movable switch blade being less than the longitudinal spacing between the arcing contacts of the impedance assemblage, and the capacitance between the arcing contacts assisting in grading the voltage lengthwise along the impedance assembly during the opening operation.

5. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing anarcuate path of travel, means effecting an axial contact-pressurereducing rotation of the switch blade during the initial portion of the opening operation, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including a plurality of resistor stacks enclosed interiorly within hollow insulating casings, a plurality of rod-shaped arcing electrodes tapped into said resistor stacks and extending laterally from the impedance assemblage adjacent said arcuate path of travel yet spaced from said arcuate path of travel, the lateral dimension of the free end of the movable switch blade being less than the longitudinal spacing between the rod-shaped arcing electrodes, and the capacitance between the arcing electrodes assisting in grading the voltage lengthwise along the impedance assemblage during the opening operation.

6. The combination in an air-break disconnecting switch of a relatively stationary contact and a swinging movable disconnect blade cooperable therewith to complete the electrical circuit through the switch, insulating support means for mounting the relatively stationary contact and the movable disconnect blade in spaced relation in the open circuit position, means causing an axial contact-prossure-reducing rotation of the movable disconnect blade during the initial portion of the opening operation, said insulating support means also supporting a stationary impedance assemblage close to the relatively stationary contact, the impedance assemblage including a plurality of hollow insulating casings, an elongated impedance element mounted interiorly Within each hollow casing, a plurality of spaced arcing contacts spaced from the path of opening movement of said movable blade and connected to said impedance elements, the lateral dimension of the free end of the movable disconnect blade being less than the longitudinal spacing between said spaced arcing contacts, the capacitance between the spaced arcing contacts assisting in grading the voltagelengthwise along the stationary impedance assemblage during the opening operation, and the impedance elements being successively inserted into series circuit during the opening operation of the disconnecting switch.

7. The combination in an air-break disconnecting switch of a relatively stationary contact and a swinging movable disconnect blade cooperable therewith to complete '9 the electrical circuit through the switch, insulating support means for mounting the relatively stationary contact and the movable disconnect blade in spaced relation in the open circuit position, means causing an axial contact-pressure-reducing' rotation of the movable disconnect blade during the initial portion of the opening operation, said insulating support means also supporting a stationary impedance assemblage close to the relatively stationary contact, the impedance assemblage including a plurality of hollow insulating casings, an elongated impedance element mounted interiorly within each hollow casing, a plurality of spaced arcing rings spaced from the path of opening movement of said movable blade and electrically connected to said impedance elements, thev lateral dimension of the free end of the movable disconnect blade being less than the longitudinal spacing between said spaced arcing rings, the capacitance between the spaced arcing rings assistingin grading the voltage lengthwise along the stationary impedance assemblage, and the impedance elements being successively inserted into series circuit during the opening operation of the disconnecting switch. I b

8. The combination of an air-break disconnecting switch of a relatively stationary contact and a swinging movable disconnect blade cooperable therewith to establish an arc, insulating support means for mounting therelatively stationary contact and the movable disconnect blade in spaced relation in the open circuit position, means causing an axial contact-pressure-reducing rotation of the movable disconnect blade during the initial portion of the opening operation, said insulating support means also supporting'a stationary impedance assemblage close to the relatively stationary contact, the impedance assemblage including a plurality of hollow insulating casings, an elongated impedance element mounted interiorly within each hollow casing, a plurality of spaced rod-like arcing electrodes extending laterally from said impedance assemblage and connected to the ends of a plurality of elongated impedance elements, said rod-like arcing electrodes spaced from the path of opening movement of said movable blade, the lateral dimension of the free end of the movable disconnect blade being less than the longitudinalspacing between said spaced rod-like arcing electrodes, the capacitance between the spaced arcing electrodes assisting in grading the voltage lengthwise along the stationary impedance assemblage, and the impedance elements being successively inserted into series circuit during the opening operation of the disconnecting switch.

9. An air-break disconnecting switch including a relatively stationary contact, insulating means for mounting a swinging movable disconnecting switch blade, the swinging movable disconnecting switch blade being cooperable with the relatively stationary contact to establish an are, means mounting an impedance assemblage adjacent the relatively stationary contact, said impedance assemblage including at least one umbrella-shaped shielding ring at one end of the assemblage, the umbrella-shaped shielding ring being spaced from the opening path of travel of the movable disconnecting switch blade, said extending toward each other and disposed at opposite ends of the impedance assemblage, said pair of umbrella-shaped shielding rings being spaced from the opening path of travel of the swinging movable disconnecting switch blade, said impedance assemblage including one or more impedance elements,-at'1east one umbrellashaped shielding ring electrically connected to one impedance element, and the one or more impedance elements being inserted serially into circuit during the opening operation. I

11. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, means for causing an axial, ice-freeing and contact-pressure-reducing rotation of the switch blade during the initial portion of the opening operation, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including a plurality of impedance sections, insulating weatherproof casing means surrounding and enclosing said impedance sections, a plurality of spaced arcing contacts connected to said impedance sections, a gap separation distance between said arcing contacts and the arcuate opening path of travel of the switch blade, the lateral dimension of the free end of the movable switch blade being less than the longitudinal spacing between said spaced arcing contacts, and the capacitance between the spaced arcing contacts assisting in grading the voltage lengthwise along the impedance assemblage.

12. An air-break disconnecting switch for high-voltage service including a pair of spaced insulator columns, a relatively stationary disconnecting contact supponted at theend of one of said pair of insulator columns, a movable disconnecting switchblade supported on the end of the other insulator column and adapted for swinging engagement and disengagement with said relatively stationary disconnecting contact to close and open the connected circuit, a pair of spaced side ring-shaped corona shields disposed on opposite sides of said relatively stationary disconnecting contact toprevent the formation of corona at said relatively stationary disconnecting contact, an impedance assemblage disposed adjacent the relatively stationary disconnecting contact and extending away therefrom generally in the direction of the path or arcuate travel of the outer free end of the swinging disconnecting switch blade, said impedance assemblage including a plurality of impedance sections, each impedance section including a hollow weatherproof casing having supporting flange means at the opposite ends thereof, a plurality of arcing electrodes associated with said supporting flange means including a stub electrode disposed relatively closely to said side ring-shaped corona shields, at least one substantially oval-shaped arcing ring more remote therefrom, and the last-mentioned substantially oval-shaped arcing ring being disposed in a plane substantially normal to the axial length of the impedance assemblage.

13. An air-break disconnecting switch for high-voltage service including apair of spaced insulator columns, a relatively stationary disconnecting contact supported at the end of one of said pair of insulator columns, a movable disconnecting switch blade supported on the end of the other insulator column and adapted for swinging engagement and disengagement with said relatively stationary disconnecting contact to close and open the connected circuit, a pair of spaced side ring shaped corona shields disposed on opposite sides of said relatively stationary disconnecting contact to prevent the formation of corona at said relatively stationary disconnecting contact, an impedance assemblage disposed adjacent the relatively stationary disconnecting contact and extending away therefrom generally in the direction of the path of arcuate travel of the outer free end of the swinging disconnecting switch blade, said impedance assemblage including a plurality of impedance sections, each impedance section including a hollow weatherproof casing having supporting flange means at the opposite ends thereof, a plurality arcing electrodes associated with said supporting flange means including a stub electrode disposed relatively closely to said side ring-shaped corona shields, at least one substantially oval-shaped arcing ring more remote therefrom, the last-mentioned substantially oval-shaped arcing ring being disposed in a plane substantially normal to the axial length of the impedance assemblage, and adjusting means associated with one of said supporting flange means to adjustably space said substantially oval-shaped arcing ring from the arcuate path of travel of the outer free end of said swinging disconnecting switch blade.

14. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including a pair of impedance sections, a pair of spaced arcing contacts at the ends of said pair of impedance sections to which the are upon opening switch movement may terminate yet spaced from said arcuate path of travel, said paid of spaced arcing contacts including a pair of spaced oval-shaped arcing rings disposed in planes substantially normal to the axial length of the impedance assemblage, and said pair of spaced oval-shaped arcing rings being employed to successively assume arcing from the end of the switch blade and to control voltage gradation axially along the impedance assemblage.

15. An air-break disconnecting switch including means defining a relatively stationary contact, a swinging movable switch blade engageable with the relatively stationary contact to complete the electrical circuit through the switch, a corona ball disposed at the outer end of the swinging switch blade, the swinging movable switch blade separating from the relatively stationary contact during the opening operation of the switch and traversing an arcuate path of travel, an impedance assemblage disposed adjacent the relatively stationary contact and extending generally therefrom in the direction of said path of travel, said impedance assemblage including one or more impedance sections, an arcing contact at one end of at least one impedance section to which the are upon opening switch movement may terminate yet spaced from said arcuate path of travel, and said arcing contact including a substantially oval-shaped arcing ring disposed in a plane substantially normal to the axial length of the impedance assemblage.

16. The combination in a high-voltage, air-break disconnecting switch of a relatively stationary jaw-type contact and a swinging movable disconnecting switch blade cooperable therewith to establish an arc, insulating support means for mounting the relatively stationary jawtype contact and the movable disconnecting switch blade in spaced relation in the open-circuit position, operating means for effecting an axial, ice-freeing rotation of the switch blade during the opening operation as well as the aforesaid swinging movement thereof, a stationary impedance assemblage stationarily mounted adjacent the jaw-type stationary contact and extending in the general direction of the opening travel of the free end of said switch blade, the impedance assemblage including adjoining impedance sections having weather-proof casings and a plurality of generally ring-shaped arcing contacts tapped into the assemblage and spaced apart, the free end of the swinging movable disconnecting switch blade clear- 12 ing said control ring contacts with spacing therebetween for facilitated unimpeded opening motion of the disconnecting switch blade, and the planes of the arcing control ring contacts being substantially normal to the axial length of the impedance assemblage.

17. The combination in a high voltage air-break disconnecting switch of a relatively stationary jaw-type contact and a swinging movable disconnecting switch blade cooperable therewith to establish an are, a corona ball disposed at the outer free end of the switch blade, insulating support means for mounting .the relatively stationary jaw-type contact and the movable disconnecting switch blade in spaced relation in the open-circuit position, operating means for effecting an axial, ice-freeing rotation of the switch blade during the opening operation as well as the aforesaid swinging movement thereof, a stationary impedance assemblage stationarily mounted adjacent the jaw-type stationary contact and extending in the general direction of the opening travel of the free end of said switch blade, the impedance assemblage ineluding adjoining impedance sections having weatherproof casings and a plurality of generally ring-shaped arcing contacts tapped into the assemblage and spaced apart, and the free end of the swinging movable disconnecting switch blade clearing said control ring contacts with spacing therebetween for facilitated unimpeded opening motion of the disconnecting switch blade, and the planes of the arcing control ring contacts being substantially normal to the axial length of the impedance assemblage.

18. The combination in a high-voltage, air-break disconnecting switch of a relatively stationary jaw-type contact and a swinging movable disconnecting switch blade cooperable therewith to establish an arc, insulating sup port means for mounting the relatively stationary jawtype contact and the movable disconnecting switch blade in spaced relation in the open-circuit position, operating means for effecting an axial, ice-freeing rotation of the switch blade during the opening operation as well as the aforesaid swinging movement thereof, a stationary impedance assemblage stationarily mounted adjacent the jaw-type stationary contact and extending in the general direction of the opening travel of the free end of said switch blade, the impedance assemblage including adjoining impedance sections having weather-proof casings and a plurality of oval-shaped arcing control rings tapped into the assemblage and spaced apart, the free end of the swinging movable disconnecting switch blade clearing said control ring contacts with spacing therebetween for facilitated unimpeded opening motion of the disconnecting switch blade, and the planes of the arcing control ring contacts being substantially normal to the axial length of the impedance assemblage.

19. The combination in a high-voltage, air-break disconnecting switch of a relatively stationary jaw-type contact and a swinging movable disconnecting switch blade cooperable therewith to establish an are, a pair of spaced, side, ring-shaped corona shields disposed on opposite sides of the relatively stationary jaw-type contact, insulating support means for mounting the relatively stationary jaw-type contact and the movable disconnecting switch blade in spaced relation in the open-circuit position, operating means for eifecting an axial, ice-freeing rotation of the switch blade during the opening operation as well as the aforesaid swinging movement thereof, a stationary impedance assemblage stationarily mounted adjacent the jaw-type stationary contact and extending in the general direction of the opening travel of the free end of said switch blade, the impedance assemblage including adjoining impedance sections having weatherproof casings and a plurality of generally ring-shaped arcing contacts tapped into the assemblage and spaced apart, the free end of the swinging movable disconnecting switch blade clearing said control ring contacts with spacing therebetween for facilitated unimpeded opening motion of the disconnecting switch blade, and the planes of the arcing control ring contacts being substantially normal to the axial length of the impedance assemblage.

20. The combination in a high-voltage, air-break disconnecting switch of a relatively stationary jaw-type contact and a swinging movable disconnecting switch blade cooperable therewith to establish an arc, insulating support means for mounting the relatively stationary jawtype contact and the movable disconnecting switch blade in spaced relation in the open-circuit position, operating means for effecting an axial, ice-freeing rotation of the switch blade during the opening operation as well as the aforesaid swinging movement thereof, a stationary impedance assemblage stationarily mounted adjacent the jaw-type stationary contact and extending in the general direction of the opening travel of the free end of said switch blade, the impedance assemblage including adjoining impedance sections having weather-proof casings and a plurality of generally ring-shaped arcing contacts tapped into the assemblage and spaced apart, metallic clamping flange means disposed between juxtaposed weatherproof casings to clamp at least a pair of arcing control rings fixedly in place, the free end of the swinging movable disconnecting switch blade clearing said control ring contacts with spacing therebetween for facilitated unimpeded opening motion of the dlisconnecting switch blade, and the planes of the arcing control ring contacts being substantially normal to the axial length of the impedance assemblage.

References Cited in the file of this patent UNITED STATES PATENTS 1,563,833 Christensen Dec. 1, 1925 1,861,129 Milliken May 31, 1932 2,586,290 Baker etal. Feb. 29, 1952 2,830,145 Killian Apr. 8, 1958 

